McArdle Sign: A Specific Sign of Multiple Sclerosis

Filippo Savoldi; Zahra Nasr; Wei Hu; Nathan D Schilaty; Adriana M Delgado; Jay Mandrekar; Kenton R Kaufman; Lawrence Berglund; Brian G Weinshenker

doi:10.1016/j.mayocp.2019.01.047

McArdle Sign: A Specific Sign of Multiple Sclerosis

Mayo Clin Proc. 2019 Aug;94(8):1427-1435. doi: 10.1016/j.mayocp.2019.01.047. Epub 2019 Jul 11.

Authors

Filippo Savoldi¹, Zahra Nasr², Wei Hu³, Nathan D Schilaty⁴, Adriana M Delgado², Jay Mandrekar⁵, Kenton R Kaufman⁴, Lawrence Berglund⁴, Brian G Weinshenker⁶

Affiliations

¹ Department of Neurology, Mayo Clinic, Rochester, MN; Postgraduate School of Radiodiagnostics, Università degli Studi di Milano, Milan, Italy.
² Department of Neurology, Mayo Clinic, Rochester, MN.
³ Department of Neurology, University of Florida, Gainesville.
⁴ Department of Orthopedics, Mayo Clinic, Rochester, MN; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN.
⁵ Department of Health Sciences Research, Mayo Clinic, Rochester, MN.
⁶ Department of Neurology, Mayo Clinic, Rochester, MN. Electronic address: weinb@mayo.edu.

PMID: 31303427
DOI: 10.1016/j.mayocp.2019.01.047

Abstract

Objective: To measure McArdle sign (rapidly reversible weakness induced by neck flexion) both qualitatively and quantitatively and to evaluate its specificity and clinical utility for diagnosis of multiple sclerosis (MS).

Patients and methods: In this prospective study, McArdle sign was evaluated by a technician blinded to diagnosis by measuring changes in finger extensor strength in successive trials of neck extension and flexion, first clinically and then with a torque measurement device. We studied 25 healthy controls and 81 patients with finger extensor weakness. Patients were not selected for having McArdle sign. Fifty-two patients had MS, 24 had other myelopathies, and 5 had peripheral nerve lesions accounting for their weakness. The study was conducted between February 1, 2016, and June 30, 2017.

Results: The median clinical McArdle sign and the 2 quantitative measures of neck flexion-induced strength reduction were greater in patients with MS than in the other groups (P<.001). Baseline strength did not confound the difference. The area under the receiver operating characteristic curve was 0.84 (95% CI, 0.75-0.93) comparing patients with MS vs healthy controls and 0.84 (95% CI, 0.75-0.93) comparing MS vs patients with other myelopathies. The 2 quantitative and 1 clinical measurement of McArdle sign by the technician who performed the quantitative testing were correlated (r=.57 and r=.58; P<.001), and in turn, the technician's and unblinded referring physician's clinical assessments were correlated (r=.58; P<.001). McArdle sign was evident in some patients who had minor disability and who were in early phases of MS.

Conclusion: McArdle sign, when defined as greater than 10% neck flexion-induced reduction in strength, is entirely specific and 65% sensitive for a diagnosis of MS when compared with other conditions that mimic MS-associated myelopathy. It may facilitate diagnosis in certain clinical situations.

Trial registration: clinicaltrials.gov Identifier: NCT03122873.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Case-Control Studies
Disease Progression
Female
Humans
Logistic Models
Magnetic Resonance Imaging / methods*
Male
Middle Aged
Multiple Sclerosis / classification
Multiple Sclerosis / diagnosis*
Multivariate Analysis
Muscle Weakness / classification
Muscle Weakness / diagnosis*
Neurologic Examination / methods*
Physical Examination / methods*
Pilot Projects
ROC Curve
Risk Assessment
Sensitivity and Specificity
Severity of Illness Index

Associated data

ClinicalTrials.gov/NCT03122873